Cell adhesion molecules are surface proteins that mediate the binding of cells to extracellular matrix and to other cells. The expression of cell adhesion molecules, which is important for the migration of leukocytes to sites of inflammation, and is partly regulated by the secretion of cytokines. We are studying the expression of cell adhesion molecules in the eye, in both animal models of ocular inflammation and human eyes with uveitis. Over the past year, we have demonstrated the expression of endothelial leukocyte adhesion molecule 1 (ELAM-1) on the corneal endothelium in Lewis rats with endotoxin-induced uveitis. Expression of ELAM-1 precedes the binding of neutrophils and the formation of keratic precipitates. In human eyes with posterior uveitis, we have shown that lymphocyte function- associated antigen 1 (LFA-1) is expressed on lymphocytes infiltrating the retina and choroid. Intercellular adhesion molecule 1 (ICAM-1), the counter receptor for LFA-1, was demonstrated on retinal pigment epithelium, on vascular endothelium, and on glial cells of the retina in areas of inflammation. Increased levels of tumor necrosis factor, which were demonstrated in eyes with uveitis, may play a role in the induction of these adhesion molecules. We have also examined the expression of adhesion molecules in eyes with intraocular lymphoma and demonstrated LFA-1 and ICAM-1 on cells from an intraocular lymphoma in a patient with AIDS. In a second intraocular lymphoma in a patient without AIDS, ICAM-1 but not LFA-1 was expressed on tumor cells. Expression of adhesion molecules on lymphoma cells may be important for the localization of the tumor in the eye.